Musannaf Ibn Abi Shayba 9:502

Sharik narrated to us, from Abu Ishaq, from Amir ibn Sa'd, who said: I entered upon Ibn Mas'ud and Qurzah ibn Ka'b, and with them were slave girls singing. I said: "Do you do this while you are companions of the Messenger of Allah, may Allah bless him and grant him peace?" He said: So he replied: "It has been permitted for us to have amusement at the time of a wedding."